On the use of simplified reactive power flow equations for purposes of fast reliability assessment

In the present paper, a new method, derived from the linearization of the reactive power flow equations, is presented and discussed. The proposed technique is able to quickly calculate voltages at load busses, as well as reactive power injections at generation busses, using the results of a preliminary ordinary DC load flow. Due to the extremely reduced computational time, this technique can be successfully used for fast reliability assessments, when a huge number of load flow scenarios, generated by a probabilistic approach like Monte Carlo techniques, must be analyzed in terms of voltage violations; the algorithm is also promising for Optimal Reactive Power Flow procedures. Two case studies, based on the IEEE RTS-96 and Poland transmission and sub-transmission network, confirm a speed-up of more than 6 times respect to the Newton-Raphson algorithm, while keeping the mean squared error of voltages within 0.5% and the maximum voltage error below 1.5% of the voltage limits.